Mac enhancement to support multi-periodic gts allocation for personal area network (pan) systems

ABSTRACT

A personal area network (PAN) coordinator ( 26 ) of a medical body area network (MBAN) ( 36 ) allocates multi-periodic guaranteed time slots (GTSs) to sensor devices ( 12, 14 ) of the MBAN ( 36 ). The PAN coordinator ( 26 ) includes a controller ( 40 ) configured to receive a request for a multi-periodic GTS from a sensor device ( 12, 14 ) of the MBAN ( 36 ). The request includes a period indicating a periodicity with which the multi-periodic GTS is requested. In response to the request, the controller ( 40 ) determines a GTS allocation including a starting frame and transmits a descriptor to the sensor device ( 12, 14 ). The descriptor includes information to identify the starting frame.

The present application relates generally to wireless communication. Itfinds particular application in conjunction with medical body areanetworks (MBANs) and will be described with particular referencethereto. However, it is to be understood that it also finds applicationin other usage scenarios and is not necessarily limited to theaforementioned application.

There is a general trend in the healthcare industry towards expandingcare services, such as patient monitoring, to general wards and evenbeyond the physical hospital boundaries. Medical body area networks(MBANs) (a.k.a., wireless body area networks) are one of the keyenabling technologies for ubiquitous monitoring services. An MBAN is awireless network of sensors around a patient used for monitoring apatient's physiological data. The clinical benefits of MBANs include:extension of monitoring into care areas that are currently unmonitored;improved healthcare workflow efficiency, safety and clinical outcome;patient mobility, comfort, and infection control; monitoring flexibilityand scalability; and reduced overall monitoring costs. This is notintended to be an exhaustive list of benefits.

With reference to FIG. 1, a typical MBAN system includes several tinysensor devices placed on a patient's body to capture physiological dataof the patient, such as heart rate and electriocardiogram (ECG) signals.The captured data is forwarded to a hub device through a short-range andlow-power MBAN. The hub device could be a local bedside monitoring unit,a cell phone, a set-top-box, or other wireless device and usually has aconnection to a backhaul network (e.g., a cellular network, a LAN,etc.), through which the collected data is further transferred to acentral monitoring system. The central monitoring system is responsiblefor analyzing patients' physiological data and provides monitoring,diagnosing or treating services in real time.

Currently, the Institute of Electrical and Electronics Engineers (IEEE)is developing wireless communication standards for MBAN applications.One example is the IEEE 802.15.4j standard in which physical (PHY)/mediaaccess control (MAC) layer enhancement features are under development toextend widely used IEEE 802.15.4 radios to better serve MBANapplications. In the IEEE 802.15.4-2006 standard, a guaranteed time slot(GTS) mechanism is defined to allow a device to operate on the channelwithin a portion of the superframe that is dedicated exclusively to thatdevice. GTSs form a contention-free period (CFP), which always appear atthe end of the active superframe, as shown in FIG. 2. Such a GTS schemeprovides a good data transfer solution for MBAN applications that haveregular, periodic data traffic and strict latency requirements, like ECGmonitoring application.

A device can request the allocation of a new GTS from a personal areanetwork (PAN) coordinator, typically the hub device, through the MACsublayer management entity (MLME)-GTS request primitive, with the GTScharacteristics set according to the requirements of the intendedapplication. Once a GTS request is received, the PAN coordinator sendsan ACK to acknowledge receipt of the GTS request. The PAN coordinatoralso checks if it has enough resource to support the new GTS allocationand makes a decision as to whether to allocate the requested GTS. If theallocation can be made, the PAN coordinator broadcasts the allocated GTSinformation as part of a GTS descriptor (including the starting timeslot and the slot length) in its beacon frame foraGtsDescPersistenceTime superframes. On receipt of the acknowledgment tothe GTS request command, the device continues to track beacons and waitsfor at most aGtsDescPersistenceTime superframes. If no GTS descriptorfor itself is received, the device assumes that its GTS request failed.Otherwise, the device uses the information included in its GTSdescriptor to locate its GTS time slots.

One challenge with the GTS scheme defined in the current IEEE 802.15.4specification is that it may not be able to support low duty cycle MBANapplications, like heart rate monitoring applications, efficiently interms of time slot usage and power consumption. The allocation of a GTSmeans that the allocated time slots are exclusively reserved for itsowner device to communicate with the PAN coordinator in every superframeafter the allocation. For example, if the PAN coordinator grants a GTSallocation of time slot 6 to device A and starts broadcasting the GTSdescriptor of that allocation in its beacon frame of superframe K, thentime slot 6 of superframe N>=K (i.e., N=K, K+1, K+2, . . . ) will bereserved for operations of device A.

For low duty cycle MBAN applications, such as blood pressure monitoringand heart rate monitoring, the IEEE 802.15.4 GTS scheme may not beefficient. With a very low data rate or duty cycle, a device in thoseapplications may only need to communicate with the PAN coordinator for avery short time period over a long time interval. That means a devicecan stay in “sleep” mode for most superframes and only wake up in itsGTS slots to do communication every tens or even hundreds ofsuperframes. This feature is very important to MBAN applications sinceit can greatly prolong the battery life of a device by putting thedevice in “sleep” mode for most of time.

However, the IEEE 802.15.4 GTS scheme reserves the allocated time slotsof every superframe following the allocation exclusively for the use ofa device even though the device doesn't need to communicate everysuperframe. Hence, the IEEE 802.15.4 GTS scheme does not use the timeslots efficiently. This is especially true for a device that only usesthe allocated time slots every tens or even hundreds of superframes.Moreover, to maintain its GTS allocation, a device may have to wake upand do some dummy communication with the PAN coordinator even though thedevice doesn't have useful data to transfer. Otherwise, the PANcoordinator may assume the device lost its communication link and willrelease its GTS allocation. This will unnecessarily increase the“wake-up” time of the device and greatly decrease its battery life,which is unacceptable to MBAN applications.

The present application provides a new and improved method whichovercomes the above-referenced problems and others.

In accordance with one aspect, a personal area network (PAN) coordinatorof a medical body area network (MBAN) allocates multi-periodicguaranteed time slots (GTSs) to sensor devices of the MBAN. The PANcoordinator includes a controller configured to receive a request for amulti-periodic GTS from a sensor device of the MBAN. The requestincludes a period indicating a periodicity with which the multi-periodicGTS is requested. In response to the request, the controller determinesa GTS allocation including a starting frame and transmits a descriptorto the sensor device. The descriptor includes information to identifythe starting frame.

In accordance with another aspect, a method allocates multi-periodicguaranteed time slots (GTSs) to sensor devices of a medical body areanetwork (MBAN). The method includes receiving a request for amulti-periodic GTS from a sensor device of the MBAN. The requestincludes a period indicating a periodicity with which the multi-periodicGTS is requested. A GTS allocation, including a starting frame, for therequest is determined and a descriptor is transmitted to the sensordevice. The descriptor includes information to identify the startingframe.

In accordance with another aspect, a frame structure is employed fortransmitting data over a medical body area network (MBAN) from a sensordevice to a hub device. The frame structure supports multi-periodicguaranteed time slots (GTSs) and includes a contention access periodaccording to IEEE 802.15.4 and a contention free period including aplurality of GTSs. A GTS of the plurality of GTSs includes an allocationto a sensor device, the allocation including a period indicating aperiodicity with which the GTS is allocated to the sensor device.

One advantage resides in reduced battery consumption for MBAN devices.

Another advantage resides in improved efficiency in GTS allocation.

Another advantage resides in backwards compatibility.

Still further advantages of the present invention will be appreciated tothose of ordinary skill in the art upon reading and understand thefollowing detailed description.

The invention may take form in various components and arrangements ofcomponents, and in various steps and arrangements of steps. The drawingsare only for purposes of illustrating the preferred embodiments and arenot to be construed as limiting the invention.

FIG. 1 illustrates a MBAN system.

FIG. 2 illustrates a superframe structure with GTSs.

FIG. 3 illustrates a superframe structure with multi-periodic GTSs.

FIG. 4 illustrates a superframe structure with multi-periodic GTSs andtime-sharing between sensor devices.

FIG. 5 illustrates the IEEE 802.15.4 GTS specification field.

FIG. 6 illustrates a variant of the IEEE 802.15.4 GTS specificationfield which is modified for multi-periodic GTS allocation.

FIG. 7 illustrates a table of possible combinations of GTS permit andmulti-periodic GTS permit flags and whether each combination supportslegacy GTS allocation and multi-periodic GTS allocation.

FIG. 8 illustrates the IEEE 802.15.4 GTS request command.

FIG. 9 illustrates the IEEE 802.15.4 GTS characteristics field.

FIG. 10 illustrates a variant of the IEEE 802.15.4 GTS characteristicsfield which is modified for multi-periodic GTS allocation.

FIG. 11 illustrates a variant of the IEEE 802.15.4 GTS request commandwhich is modified for multi-periodic GTS allocation.

FIG. 12 illustrates a multi-periodic characteristics field.

FIG. 13 illustrates a superframe structure with multi-periodic GTSs andtime-sharing between sensor devices.

FIG. 14 illustrates the IEEE 801.15.4 GTS descriptor.

FIG. 15 illustrates the IEEE 801.15.4 GTS descriptor which is modifiedfor multi-periodic GTS allocation.

FIG. 16 illustrates a block diagram of a MBAN system.

A multi-periodic GTS allocation with a period of M (M>1) starting fromsuperframe K means the allocated time slot(s) are exclusively reservedfor the device to communicate with the PAN coordinator every Msuperframes starting from superframe K (i.e., N=K, K+M, K+2M, K+3M, . .. ), as shown in FIG. 3. With multi-periodic GTS allocation, a sensordevice can pick up a proper period M based on its data traffic, suchthat it only needs to wake up for communication when it has data totransfer. Therefore, the multi-periodic GTS allocation can improvebattery life of a sensor device in low duty cycle MBAN applications.

Furthermore, for the superframes with N≠K, K+M, K+2M, K+3M, . . . , theallocated time slot(s) are available for GTS allocations to otherdevices. In other words, multiple GTS allocations for different devicescan use the same time slot(s) in a time sharing way. One example isgiven in FIG. 4, where GTS1 and GTS2, both of which have M=2, share thesame time slot. In superframe N=K+2*i, i=0, 1, . . . , the allocatedtime slot is used for GTS1, while in superframe N=K+1+2*i, i=0, 1, . . ., the same allocated time slot is used for GTS2. Therefore, the GTS timeslot resources are used more efficiently with multi-periodic GTSallocation.

In view of the foregoing, a multi-periodic GTS allocation scheme isadded to IEEE 802.15.4 to improve the efficiency of IEEE 802.15.4 forlow duty-cycle MBAN applications. New GTS specification and GTS requestcommands are defined to support multi-periodic GTS allocationrequest/grant operations, as described below. The multi-periodic GTSallocation scheme advantageously achieves good legacy compatibility withcurrent IEEE 802.15.4 devices/implementations, which allows new IEEE802.15.4j devices and legacy IEEE 802.15.4 devices to work in the sameMBANs.

The MAC enhancement to IEEE 802.15.4 uses one reserved bit of the GTSspecification field transmitted in beacon frames to indicate whethermulti-periodic GTS allocation is supported by the PAN coordinator. Thecurrent IEEE 802.15.4 GTS specification field is defined as shown in theFIG. 5. The field includes 8 bits, where bits 0-2 are employed for a GTSdescriptor count, bits 3-6 are reserved and bit 7 is employed for a GTSpermit flag. To allow for multi-periodic GTS allocation, one of thereserved bits is employed for a multi-periodic GTS permit flag, as shownin FIG. 6. This flag indicates whether the PAN coordinator supportsmulti-periodic GTS allocation.

With reference to FIG. 7, a table illustrates the possible combinationsof the multi-periodic GTS permit bit (bit 6) and the GTS permit bit (bit7) and whether the combinations permit legacy GTS allocation andmulti-periodic GTS allocation. Legacy GTS allocation is GTS allocationdefined in IEEE 802.15.4, which allocates the time slots to a device inevery superframe, and multi-periodic GTS allocation is as describedabove. As shown, when both the multi-periodic GTS permit bit and the GTSpermit bit are ‘0’, neither legancy GTS allocation nor multi-periodicGTS allocation are permitted. Also, when the multi-periodic GTS permitbit is ‘0’ and the GTS permit bit is ‘1 ’, legacy GTS allocation ispermitted, but multi-periodic GTS allocation is not permitted. Further,when the multi-periodic GTS permit bit is ‘1’ and the GTS permit bit is‘1’, legacy GTS allocation and multi-peridic GTS allocation arepermitted. The combination that the multi-periodic GTS permit bit is ‘1’and the GTS permit bit is ‘0’ is reserved, which means this combinationis not valid and should not be used.

A PAN coordinator broadcasts whether it supports legacy GTS allocationand multi-periodic GTS allocation in its beacon frames by setting themulti-periodic GTS permit bit (bit 6) and the GTS permit bit (bit 7)properly. On receipt of beacon frames, a sensor device determineswhether legacy GTS allocation or multi-periodic GTS allocation aresupported by its PAN coordinator. If a device and its PAN coordinatorboth support multi-periodic GTS allocation, then the device can use amulti-periodic request command to request a multi-periodic GTSallocation when needed.

The MAC enhancement further uses an enhanced GTS request command. Inother words, in order to support multi-periodic GTS allocation, the GTSrequest command is updated. The parameter M (M>1) is the requested GTSperiod and the parameter K specifies the first superframe that thedevice wants to have the allocated time slot(s) available for operation.These parameters need to be included in the GTS request command. Theformat for the current IEEE 802.15.4 GTS request command is illustratedin FIG. 8. The request includes 7 octets for a MAC header (MHR), 1 octetfor a command frame identifer, and 1 octet for GTS characteristics. TheGTS characteristics field provides information about the requested timeslots and is illustrated in FIG. 9. Bits 0-3 are employed for a GTSlength, bit 4 is employed for a GTS direction, bit 5 is employed for acharacteristics type and bits 6 & 7 are reserved.

In order to support multi-periodic GTS request, the GTS characteristicsfield is modified as shown in FIG. 10. In the new format, one reservedbit (bit 6) is used as a multi-periodic request indicator. If this bitis set to ‘0’, then the current request is an IEEE 802.15.4 legacy GTSrequest command. If the bit is set to ‘1’, then the current request is amulti-periodic GTS request command and there will be one more octetfollowing the GTS characteristics that provides the required informationabout the GTS period M and the starting superframe K. This newmulti-periodic GTS request command with an additional octet has a formatas shown in FIG. 11. The additional octet is employed for amulti-periodic GTS characteristics field. In other embodiments, the PANcoordinator can determine whether a received GTS request command is amulti-periodic GTS request command based on the length of the receivedGTS request command without using one reserved bit (bit 6) as amulti-periodic request indicator. If the length is 9 octets, then theGTS request command is a legacy GTS request command, while if the lengthis 10 octets, then the GTS request command is a multi-periodic GTSrequest command,

The multi-periodic GTS characteristics field has a format as shown inFIG. 12 and includes two fields, a starting superframe offset rangefield and a multi-periodic GTS period order field. The startingsuperframe offset range field S occupies bits 0-3 and is greater than orequal to ‘0’ and less than or equal to ‘15’ (i.e., 0≦S≦15). This fieldindicates that the device requests to have its GTS allocation start fromsuperframe K, which is no later than S superframes after the nextsuperframe. S =0 indicates that the GTS allocation should start from thenext superframe. The actual starting superframe K is determined by thePAN coordinator based on the current GTS slot resource status. K shouldsatisfy 0≦K≦S. The multi-periodic GTS period order field G occupies bits4-7 and is greater than or equal to ‘0’ and less than or equal to ‘15’(i.e., 0≦G≦15). In other embodiments, the multi-periodic GTS periodorder field occupies bits 4-6, where 0≦G≦7. This field provides theperiod of the requested multi-periodic GTS allocation.

The period M is defined as M=2^((G+1)). Suitably, the period M is apower of 2 because this makes GTS management and reallocation mucheasier. For example, it is easy to use only one GTS time slot to supporttwo multi-periodic GTS allocations with M=4 (GTS2 and GTS3) and onemulti-periodic GTS allocation with M=2 (GTS1) in a time-sharing way, asshown in FIG. 13. In some embodiments, a complete binary tree is used tofacilitate scheduling in this manner. If M is allowed to be any positiveinteger that is larger than 1, then it will make time sharing of a GTStime slot among multiple multi-periodic GTS allocations difficult. This,in turn, has the affect of reducing the GTS time slot usage efficiency.For example, it is impossible to share the same time slot between amulti-periodic GTS allocation with M=3 and a multi-periodic GTSallocation with M=5. Two time slots would be needed to support the twomulti-periodic GTS allocations.

In some embodiments, the PAN coordinator dynamically adjusts the periodsof GTS allocations when demand exceeds available GTSs. For example, ifthe PAN coordinator is servicing too many devices to provide all thedevices the requested GTS allocations, the PAN coordinator can increasethe periods of existing GTS allocations to allow all the devices toreceive GTS allocations. Suitably, the lower bound on a GTS allocationis the requested period and the upper bound is set by the capabilitiesof the device and/or PAN coordinator.

With the above proposed update, the legacy IEEE 802.15.4 GTS requestcommand can be reused to support a multi-periodic GTS request. Anotheroption would be to define a new multi-periodic GTS request command withthe format defined in FIG. 11. In this option, a unique command frameidentifier is assigned to the multi-periodic request command. Based onthe unique command frame identifier, a PAN coordinator can determinewhether a received frame is a multi-periodic GTS request command andprocess it properly. According to either option, GTS length in the GTScharacteristics field can still be used to give periodic GTS with one ormore continguous slots.

The MAC enhancement further uses an enhanced GTS descriptor. Once a PANcoordinator receives a multi-periodic GTS request command and decides togrant such a GTS, it generates a GTS descriptor and transmits it in itsbeacon frames to notify the requesting device about the granted GTSallocation. The GTS descriptor defined in IEEE 802.15.4 has a format asshown in FIG. 14. The GTS descriptor is 24 bits in size, where bits 0-15are employed to identify a device short address, bits 16-19 are employedto specify a GTS starting slot, and bits 20-23 are employed to specify aGTS length. However, the legacy GTS description cannot provideinformation about the starting superframe K, which is needed for therequesting device to determine in which superframes (i.e., beaconsuperframe number (BSM)=K+i*M, i=0, 1, 2, . . . ) the allocated timeslots are available for use. Therefore, for a GTS descriptor of amulti-periodic GTS allocation, the GTS length field is replaced with aGTS starting BSN, as shown in FIG. 15.

In the multi-periodic GTS case, the GTS length by default is the onerequested by a device (i.e., the GTS length in the GTS characteristicsfield in the GTS request command) and is not included in the GTSdescriptor. Instead, the GTS starting BSN is included there to providethe information about the starting superframe K. In some embodiments,such superframe is the first superframe after the current superframethat the periodic GTS slot is available to be used by the requestingdevice and that has a BSN with the four least significant bits equal tothe GTS length field (bits 20-23). Based on the current superframe BSNand the GTS starting BSN field, the requesting device can calculate K.For example, if a multi-periodic GTS descriptor is transmitted in thebeacon frame of superframe 26 (011010 in binary format) and its GTSstarting BSN is set to 0000, then that means the starting superframeK=32 (100000) since superframe 32 is the first superframe aftersuperframe 26 that has BSN (i.e., 32) with the four least significantbits equal to 0000. In other embodiments, the GTS length field (bits20-23) represents an offset S (0≦S≦15) and the first superframe afterthe current superframe that the periodic GTS slot is available to beused by the requesting device is S superframes after the nextsuperframe. S=0 indicates that the GTS allocation starts from the nextsuperframe.

The proposed modification to the GTS descriptor keeps the length of GTSdescriptor unchanged and thus keeps the length of the beacon framestructure, which is important for legacy compatibility. If the beaconstructure is changed, then the legacy IEEE 802.15.4 devices cannotcorrectly decode the information included in the beacon frame. In viewof the foregoing, an approach for implementing multi-periodic GTS forIEEE 802.15.4 is provided. The approach requires minimal changes bymaking use of unused bits and redefining existing fields when periodicGTS is used. Only the GTS request reqirest an additional octet whenperiodic GTS is used. Because the changes are minimal, the approachallows backwards compatibility. Further, although not discussed above,it is to be understood that PAN coordinators need to store informationon more than 7 GTSs since the allocation may change from one superframeto the next. Even more, detection of GTS expiration will need to take into account periodic GTS.

With reference to FIG. 16, an MBAN system 10 employing themulti-periodic GTS variant of IEEE 802.15.4, described above, isprovided. The system 10 includes a plurality of sensor devices 12, 14that capture physiological data of an associated patient 16, such asheart rate, respiration rate, blood pressure, ECG signals, and so forth.The sensor devices 12, 14 are typically disposed on the exterior of thepatient 16. However, in some embodiments, the sensor devices 12, 14 areadditionally or alternatively disposed in the patient 16 and/orproximate to the patient 16.

Each of the sensor devices 12, 14 includes a controller 18, 20 and atleast one sensor 22, 24 for measuring at least one physiologicalparameter of the patient 16. The controllers 18, 20 capture thephysiological data using the sensors 22, 24 and transmit the capturedphysiological data to a hub device 26 using corresponding communicationunits 28, 30 of the sensor devices 12, 14. In some embodiments, at leastone of the controllers 18, 20 buffers the captured physiological data incorresponding memories 32, 34 of the sensor devices 12, 14 until theamount of buffered physiological data exceeds a predetermined amount.

The communication units 28, 30 communicate with the hub device 26 overan MBAN 36 formed from the multi- periodic GTS variant of IEEE 802.15.4.Suitably, at least one of the sensor devices 12, 14 takes advantage ofthe enhancement and employs a multi-periodic GTS for communicating withthe hub device 26. This sensor device includes a period M (M>1) and anidentification of a start frame for the GTS allocation, which istailored to the specific MBAN application of the sensor device. Thestart frame can be identified by, for example, a frame offset from thecurrent frame or an upper bound on the frame offset from the currentframe. The period and the identification are provided to the PANcoordinator of the MBAN 36 when the sensor device requests the GTSallocation.

The hub device 26 relays the captured physiological data from the sensordevices 12, 14 to a central monitoring station 38. Further, the hubdevice 26 typically acts as a PAN coordinator for the MBAN 36. Inembodiments, where the hub device 26 does not act as a PAN coordinator,another device of the MBAN 36 does so, such as one of the sensor devices12, 14. The hub device 26 is typically disposed proximate to the patient16. Further, the hub device 26 is typically one of a local bedsidemonitoring unit, a cell phone, a set-top-box, or other wireless device.

The hub device 26 includes a controller 40 and a first communicationunit 42. The first communication unit 42 communicates with the sensordevices 12, 14 using the MBAN 36, which, as noted above, is formed froma variant of the IEEE 802.15.4 specification enhanced to supportmulti-periodic GTS allocation. Using the first communication unit 42,the controller 40 typically acts as the PAN coordinator for the MBAN 36.In doing so, the controller 40 controls the first communication unit 42to set up the MBAN 36, associate/disassociate the sensor device 12, 14with the MBAN, allocate GTSs, including multi-periodic GTSs, to thesensor devices 12, 14, and so on. Suitably, controller 40 allocates amulti-periodic GTS based on a received period and identification of astart frame.

The controller 40 further receives the captured physiological data fromthe sensors 12, 14 using the first communication unit 42 and transmitsthe received physiological data to the central monitoring station 38using a second communication unit 44 of the hub device 26. In someembodiments, upon receiving the captured physiological data, thecontroller 40 immediately relays it to the central monitoring station38. In other embodiments, the controller 40 buffers the receivedphysiological data in a memory 46 of the hub device 26 until the amountof buffered physiological data exceeds a predetermined amount. Suitably,at least one of the sensor devices 12, 14 transmits the data to the hubdevice 26 using a multi-periodic GTS. The second communication unit 44of the hub device 26 communicates with the central monitoring station 38using a second communication network 48, such as a wide area network, alocal area network, and so on. The second communication network 48 canbe wired and/or wireless, but is typically wireless to allow the hubdevice 26 to remain mobile.

The central monitoring station 38 facilitates monitoring of the patient16 for degradation using the physiological data captured by the sensordevices 12, 14. Further, although not illustrated, the centralmonitoring station 38 is typically employed for monitoring thephysiological data captured by sensor devices of other MBANscorresponding to other patients.

The central monitoring station 38 includes a controller 50 and acommunication unit 52. The controller 50 receives the capturedphysiological data from the hub device 26. Upon receiving thephysiological data, in some embodiments, the controller 50 determineswhether to issue an alarm by matching the received physiological data toalarm criteria. For example, in some embodiments, an alarm may be issuedif at least one physiological parameters exceeds thresholds. It iscontemplated that the alarm criteria can take in to account the presentvalues of physiological parameters, as well as trends of physiologicalparameters. Further, upon receiving the physiological data, in someembodiments, the received physiological data is displayed on a displaydevice 54 of the central monitoring station 38.

As used herein, a memory includes one or more of a non-transientcomputer readable medium; a magnetic disk or other magnetic storagemedium; an optical disk or other optical storage medium; a random accessmemory (RAM), read-only memory (ROM), or other electronic memory deviceor chip or set of operatively interconnected chips; an Internet/Intranetserver from which the stored instructions may be retrieved via theInternet/Intranet or a local area network; or so forth. Further, as usedherein, a processor includes one or more of a microprocessor, amicrocontroller, a graphic processing unit (GPU), anapplication-specific integrated circuit (ASIC), a field-programmablegate array (FPGA), and the like; a controller includes a memory and aprocessor; and a display device includes one or more of a LCD display,an LED display, a plasma display, a projection display, a touch screendisplay, and the like.

The invention has been described with reference to the preferredembodiments. Modifications and alterations may occur to others uponreading and understanding the preceding detailed description. Forexample, while the present disclosure is described in conjunction withIEEE 802.15.4, it is to be appreciated that the proposed scheme is moregenerally applicable to the MAC protocol of MBANs or other sensornetwork systems. It is intended that the invention be constructed asincluding all such modifications and alterations insofar as they comewithin the scope of the appended claims or the equivalents thereof.

1. A personal area network (PAN) coordinator of a medical body areanetwork (MEAN) for allocating multi-periodic guaranteed time slots(GTSs) to sensor devices of the MBAN, said PAN coordinator comprising: acontroller configured to: receive a request for a multi-periodic GTSfrom a sensor device of the MBAN, said request including a periodindicating a periodicity with which the multi-periodic GTS is requested;determine a GTS allocation for the request, the GTS allocation includinga starting frame; and, transmit a descriptor to the sensor device, thedescriptor including information to identify the starting frame.
 2. ThePAN coordinator according to claim 1, wherein the controller is furtherconfigured to: broadcast an indication of support for a multi-periodicGTS allocation scheme.
 3. The PAN coordinator according to claim 1,wherein the controller is further configured to: track current GTSallocations, wherein the determination is based on current GTSallocations.
 4. The PAN coordinator according to claim 1, wherein thecontroller is further configured to: communicate data with the sensordevice every M frames starting from the starting frame, where M is theperiod.
 5. The PAN coordinator according to claim 1, wherein the periodis a power of two.
 6. The PAN coordinator according to claim 1, whereinthe period is greater than one.
 7. The PAN coordinator according toclaim 1, wherein the request further includes an offset range for thestarting frame.
 8. The PAN coordinator according to claim 1, wherein theinformation to identify the starting frame includes a starting beaconframe number.
 9. The PAN coordinator according to claim 1, wherein thesensor device time shares the multi-periodic GTS with another sensordevice.
 10. The PAN coordinator according to claim 1 , wherein the PANcoordinator communicates with the sensor device using IEEE 802.15.4modified to support multi-periodic GTSs.
 11. The PAN coordinatoraccording to claim 1, wherein the PAN device receives data from thesensor device using a frame structure, the frame structure comprising: acontention access period according to IEEE 802.15.4; and, a contentionfree period including a plurality of GTSs, as GTS of the plurality ofGTSs including an allocation to a sensor device, the allocationincluding a period indicating a frequency with which the GTS isallocated to the sensor device.
 12. A method for allocatingmulti-periodic guaranteed time slots (GTSs) to sensor devices of amedical body area network (MBAN), said method comprising: receiving arequest for a multi-periodic GTS from a sensor device of the MBAN, saidrequest including a period indicating a periodicity with which themulti-periodic GTS is requested; determining a GTS allocation for therequest, the GTS allocation including a starting frame; and,transmitting a descriptor to the sensor device the descriptor includinginformation to identify the starting frame.
 13. The method according toclaim 12, further including: broadcasting an indication of support for amulti-periodic GTS allocation scheme.
 14. The method according to claim12, further including: tracking current GTS allocations, wherein thedetermination is based on current GTS allocations.
 15. The methodaccording to claim 12, further including: communicate data with thesensor device every M frames starting from the starting frame, where Mis the period.
 16. The method according to claim 12, wherein the periodis a power of two.
 17. The method according to claim 12, wherein therequest further includes an offset range for the starting frame.
 18. Themethod according to claim 12, further including: communicating with thesensor device using IEEE 802.15.4 modified to support multi-periodicGTSs.
 19. A non-transitory computer readable medium carrying computercode which controls one or more processing devices to perform the methodaccording to claim
 12. 20. A frame structure for transmitting data overa medical body area network (MBAN) from a sensor device to a hub device,the frame structure supporting multi-periodic guaranteed time slots(GTSs) and comprising: a contention access period according to IEEE802.15.4; and, a contention free period including a plurality of GTSs, aGIS of the plurality of GTSs including an allocation to a sensor device,the allocation including a period indicating a periodicity with whichthe GTS is allocated to the sensor device.